This invention relates to an electrical connector and, in particular, to an insulator in the electrical connector. The term “electrical connector” is merely referred to as “connector”, hereinafter.
A known connector has an insulator, which comprises a holding portion for holding contact pins and a plate like portion formed integral with the holding portion. The plate like portion has inner and outer surfaces perpendicular to a first direction and is elongated in a second direction perpendicular to the first direction. The plate like portion is provided with a plurality of grooves, which are formed in the inner surface of the plate like portion. Each groove extends in a third direction perpendicular to the first and the second directions. The grooves are arranged in the second direction so that ridges are formed between the respective neighboring grooves in the second direction. In other words, the plate like portion has a cross section of square waves in a plane perpendicular to the third direction. The inner surface of the plate like portion faces the contact pins under the assembled state of the connector, and the grooves are positioned in correspondence with the respective contact pins held by the insulator.
An insulator having a complex shape as mentioned above is formed by an injection molding process, wherein anisotropic resin such as liquid crystal polymer is used as material of the insulator. The liquid crystal polymer is excellent in heat resistance and also has a property difficult to vary with time. On the other hand, because of its anisotropy, the liquid crystal polymer expands or contracts upon high temperature heating or cooling in accordance with alignment of the material.
There is one problem that an undesirable curve occurs at a molded insulator.
Because of the square-waves cross-section of the insulator, there is a large difference between expansion/contraction coefficients on the inner and the outer surfaces of the plate like portion. The expansion/contraction coefficient difference causes the undesirable curve of the insulator.
In addition, because of the elongated shape of the plate like portion, it is often difficult for resin to flow into a metal mold smoothly upon injection molding. As a result, residual stress might occur in the molded insulator. Such residual stress also causes the undesirable curve of the insulator.